/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.socket.server.standard;

import java.util.Arrays;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.servlet.ServletContext;
import javax.websocket.DeploymentException;
import javax.websocket.server.ServerContainer;
import javax.websocket.server.ServerEndpoint;
import javax.websocket.server.ServerEndpointConfig;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.SmartInitializingSingleton;
import org.springframework.context.ApplicationContext;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.web.context.support.WebApplicationObjectSupport;

/**
 * Detects beans of type {@link javax.websocket.server.ServerEndpointConfig} and registers
 * with the standard Java WebSocket runtime. Also detects beans annotated with
 * {@link ServerEndpoint} and registers them as well. Although not required, it is likely
 * annotated endpoints should have their {@code configurator} property set to
 * {@link SpringConfigurator}.
 *
 * <p>When this class is used, by declaring it in Spring configuration, it should be
 * possible to turn off a Servlet container's scan for WebSocket endpoints. This can be
 * done with the help of the {@code <absolute-ordering>} element in {@code web.xml}.
 *
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @see ServerEndpointRegistration
 * @see SpringConfigurator
 * @see ServletServerContainerFactoryBean
 * @since 4.0
 */
public class ServerEndpointExporter extends WebApplicationObjectSupport
        implements InitializingBean, SmartInitializingSingleton {

    @Nullable
    private List<Class<?>> annotatedEndpointClasses;

    @Nullable
    private ServerContainer serverContainer;


    /**
     * Explicitly list annotated endpoint types that should be registered on startup. This
     * can be done if you wish to turn off a Servlet container's scan for endpoints, which
     * goes through all 3rd party jars in the, and rely on Spring configuration instead.
     *
     * @param annotatedEndpointClasses {@link ServerEndpoint}-annotated types
     */
    public void setAnnotatedEndpointClasses(Class<?>... annotatedEndpointClasses) {
        this.annotatedEndpointClasses = Arrays.asList(annotatedEndpointClasses);
    }

    /**
     * Set the JSR-356 {@link ServerContainer} to use for endpoint registration.
     * If not set, the container is going to be retrieved via the {@code ServletContext}.
     */
    public void setServerContainer(@Nullable ServerContainer serverContainer) {
        this.serverContainer = serverContainer;
    }

    /**
     * Return the JSR-356 {@link ServerContainer} to use for endpoint registration.
     */
    @Nullable
    protected ServerContainer getServerContainer() {
        return this.serverContainer;
    }

    @Override
    protected void initServletContext(ServletContext servletContext) {
        if (this.serverContainer == null) {
            this.serverContainer =
                    (ServerContainer) servletContext.getAttribute("javax.websocket.server.ServerContainer");
        }
    }

    @Override
    protected boolean isContextRequired() {
        return false;
    }

    @Override
    public void afterPropertiesSet() {
        Assert.state(getServerContainer() != null, "javax.websocket.server.ServerContainer not available");
    }

    @Override
    public void afterSingletonsInstantiated() {
        registerEndpoints();
    }


    /**
     * Actually register the endpoints. Called by {@link #afterSingletonsInstantiated()}.
     */
    protected void registerEndpoints() {
        Set<Class<?>> endpointClasses = new LinkedHashSet<>();
        if (this.annotatedEndpointClasses != null) {
            endpointClasses.addAll(this.annotatedEndpointClasses);
        }

        ApplicationContext context = getApplicationContext();
        if (context != null) {
            String[] endpointBeanNames = context.getBeanNamesForAnnotation(ServerEndpoint.class);
            for (String beanName : endpointBeanNames) {
                endpointClasses.add(context.getType(beanName));
            }
        }

        for (Class<?> endpointClass : endpointClasses) {
            registerEndpoint(endpointClass);
        }

        if (context != null) {
            Map<String, ServerEndpointConfig> endpointConfigMap = context.getBeansOfType(ServerEndpointConfig.class);
            for (ServerEndpointConfig endpointConfig : endpointConfigMap.values()) {
                registerEndpoint(endpointConfig);
            }
        }
    }

    private void registerEndpoint(Class<?> endpointClass) {
        ServerContainer serverContainer = getServerContainer();
        Assert.state(serverContainer != null, "No ServerContainer set");
        try {
            if (logger.isInfoEnabled()) {
                logger.info("Registering @ServerEndpoint class: " + endpointClass);
            }
            serverContainer.addEndpoint(endpointClass);
        } catch (DeploymentException ex) {
            throw new IllegalStateException("Failed to register @ServerEndpoint class: " + endpointClass, ex);
        }
    }

    private void registerEndpoint(ServerEndpointConfig endpointConfig) {
        ServerContainer serverContainer = getServerContainer();
        Assert.state(serverContainer != null, "No ServerContainer set");
        try {
            if (logger.isInfoEnabled()) {
                logger.info("Registering ServerEndpointConfig: " + endpointConfig);
            }
            serverContainer.addEndpoint(endpointConfig);
        } catch (DeploymentException ex) {
            throw new IllegalStateException("Failed to register ServerEndpointConfig: " + endpointConfig, ex);
        }
    }

}
